Clinical assessments for Parkinson's disease depend on clinician-administered scales, which have limitations in sensitivity and real-world applicability. Wearable inertial sensors offer a promising approach for objective and continuous monitoring of PD motor symptoms. This study aimed to evaluate the feasibility and accuracy of a magneto-inertial wearable device in detecting key PD motor manifestations-tremor, akinesia, and dyskinesia-on an individual movement basis. Ten PD patients undergoing pre-surgical evaluation for deep brain stimulation were included in a pilot multicentric study. Participants performed a Levodopa challenge test while wearing an inertial measurement unit on the most affected wrist and ankle. MDS-UPDRS Part III and video recordings were obtained to compare sensor performance to expert evaluations. Algorithms analyzed acceleration and angular velocity data to detect tremor, akinesia and dyskinesia. The sensor demonstrated high sensitivity (100%) and specificity (≥ 93%) for tremor and akinesia detection, with an overall accuracy exceeding 94%. Performance metrics were less promising for dyskinesia detection. Levodopa significantly reduced tremor (p = 0.0247) and increased dyskinesia (p = 0.0169), confirming sensor responsiveness to pharmacological effects. Magneto-inertial wearable device showed promising accuracy for the objective assessment of PD motor symptoms in a controlled environment. These findings support further validation in real-life conditions.